EPA Special Investigative Audit Report, WTC Site, Nov 2001

NYC 9/11 Public Portal Document

RESULTS

The results for individual analytes and analyte classes are presented below. Three (3) attachments have also been provided at the end of this document. Attachment 1 briefly summarizes the results reported to-date for all 497 analytes currently in the database to enable users of this report to obtain a quick reference of significant characteristics of any specific analyte. The dates of sample collection, number of samples, numbers of detects, high concentrations with dates and locations, and MDLs are information included in these summary descriptions. Attachment 2 contains EPA EnviroMapper maps identifying monitoring locations, and Attachment 3 contains trend charts for specific analytes.

Benzene and Other Volatile Organic Compounds (VOCs)

The VOC results in the NYC Response database are updated every 2-3 days. The results for twelve (12) select VOCs in air, including benzene, toluene, styrene, ethylbenzene, chlorobenzene, tetrahydro furan (THF), 2-butanone, propylene, chloromethane, trichlorofluoromethane (Freon 11), dichlorodifluoromethane (Freon 12), and chlorodifluoromethane (Freon 22), from the WTC North and South Towers are presented in the following section and listed in Tables 1 and 2. Note that on several days and for several analytes, more than one (1) sample result has been recorded. All of the VOC data recorded in the NYC Response database as of November 17"’ has been included. In the case of the VOCs, sample results through November 13"' are recorded in the database and reported here.

In the NYC Response database, the majority of VOCs detected in air from the WTC North and South Tower sites are hydrocarbons, including aromatices, ketones, alkenes, and others. With the exception of chloromethane and chlorobenzene, we have not found halogenated VOC results in the NYC Response database at levels which compare to the hydrocarbon concentrations. In all of the Lower Manhattan sites examined, the concentrations of benzene and toluene in air appear to maximize at the WTC North Tower Center where the highest concentrations reported were on October S*, October 11'*', and more recently on November 7"’, 8"’, and 9'*’. The highest benzene in air value was 180,000 ppb on November 8*. For styrene, a high value of 180,000 ppb was reported on October 11‘\

Our initial calculations indicate that the benzene results from the WTC North and South Tower sites appear largely unrelated with a correlation coefficient of 0.1779 over the thirty-two (32) days with reported values for both sites. This calculation is subject to revision based on more in-depth evaluation of sampling times.

The highest concentration of 1,3-butadiene, an indicator of aliphatic fuel combustion, was 9,200 ppb on November 8''’ from the North Tower Center. Most (192 of 204) of the results for this compound through November 8"’ were ‘not detected’ at less than 20 ppb.

Chloromethane was found at concentrations as high as 47,000 ppb on October 20"* at the WTC North Tower Center. The results for the three (3) Freons are more intermittent and variable. Chlorodifluoromethane (Freon 22) results are available starting on October 26'’’. A high value of 960 ppb was reported for chlorodifluoromethane (Freon 22) on November 1” at the

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